Newton's Blog An Alien Planet We Could Actually Visit? Posted by _Tom Hartsfield_ (http://www.realclearscience.com/authors/tom_hartsfield/) December 19, 2013 Will man ever leave a footprint on a planet belonging to a distant sun? There are very few stars close enough to permit a feasible journey, and we are just beginning to uncover whether these stars have their own “solar systems ” of planets. This week astronomers announced the possible discovery of a new planet orbiting a nearby star system; if further observations agree, this will be the closest extra-solar planet ever found. Its star system, however, is vastly different from our own. An international team of astronomers _published a report this month_ (http://arxiv.org/pdf/1312.1303v2.pdf) detailing the structure of the _binary brown dwarf system WISE J104915.57-531906.1_ (http://en.wikipedia.org/wiki/WISE_1049-5319) , less intractably called Luhman 16AB. This system consists of two stars (a _spectral class_ (http://en.wikipedia.org/wiki/Stellar_classification) L object called A and a spectral class T object B), which are trapped orbiting one another. (This is called a bound orbit, meaning that neither star will escape or be ejected from the system.) An extremely detailed analysis of the stars’ positions over two months revealed a small wobble, or perturbation in their orbits. This is likely due to the presence of a planet in the system, exerting its own gravitational forces. Exoplanets -- planets beyond our own solar system -- are now being found by the bucketful. Our closest stellar neighbors, such as _Alpha Centauri_ (http://en.wikipedia.org/wiki/Alpha_Centauri#Planets) and _Barnard’s star_ (http://en.wikipedia.org/wiki/Barnard's_Star#Claims_of_a_planetary_system) , have long been targets of fruitless exoplanet searches. Now that thousands of exoplanets have been found, it seems likely that few or no planets orbit these stars. The only promising candidate is a possible planet just larger than earth circling nearby Alpha Centauri. Unfortunately, the planet orbits closer to its star than Mercury to our sun; it is probably a searing hot oven infertile for life, capable of melting a visiting spacecraft in temperatures of 2200 degrees Fahrenheit. Our sun and Alpha Centauri are average main-sequence stars, very similar to one another. The twin suns of Luhman 16AB are brown dwarfs: balls of gas too small to fuse hydrogen in their cores and burn brilliantly, yet too massive to cool off and settle as gas giants like our Jupiter. Compare: The Sun, three types of brown dwarf stars, and Jupiter. (via _Caltech_ (http://coolcosmos.ipac.caltech.edu/images/52) ) Most stars vastly outshine these in-betweens: their absolute magnitude, or brightness, is roughly three million times dimmer than our modest sun. Luhman 16 A and B are just warm enough to glow, primarily in the redder visible and infrared regions of the spectrum. They would probably appear red (larger L-spectral class) or magenta (smaller colder T class) to our eyes. According to _Henri Boffin_ (http://www.eso.org/~hboffin/) , the lead author of the study, these stars could only warm a planet closer to them than our moon to the earth. The planet possibly found by this study, orbiting much further from its star, would be very cold on the outside. As a gas giant it would likely heat its lower atmosphere from within, however. Want to go for a visit? It will be feasible someday to see a planet only 6.6 light years away. A space mission could theoretically arrive at the planet with only a roughly 8-year journey. Why the extra years? Speeding up and slowing down from near light-speed takes a long time. A spacecraft accelerating with the strength of earth’s gravity (“one g”) would take about an entire earth year to get up to speed, and the same to stop again. Some integral calculus divines the total time to be eight years, one month, and a few days each way. That’s a long flight! Of course it’s still nothing compared to the millennia the journey would require with our fastest current space ships. Still, this is a reasonable bet for the closest planet we might visit in the future. -- -- Centroids: The Center of the Radical Centrist Community <[email protected]> Google Group: http://groups.google.com/group/RadicalCentrism Radical Centrism website and blog: http://RadicalCentrism.org --- You received this message because you are subscribed to the Google Groups "Centroids: The Center of the Radical Centrist Community" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
